As communication technology is developing, digital image processing devices (for example, smart phones, tablet PCs, smart cameras, digital cameras, or the like) are used in various fields due to their use convenience and portability.
The digital image processing device may include a function for satisfying consumers' needs to easily take photos and videos of high quality and high pixel. For example, the digital image processing device provides an Auto Focusing (AF) function to automatically set focus of a subject without requiring a user's specific operation.
In general, when the digital image processing device takes portraits, the AF function provided by the digital image processing device may automatically set focus based on a face area of a subject which is detected through a Face Detection (FD) function. However, when focus is set based on the face area of the subject, the accuracy of the AF of the digital image processing device may be reduced since the face area of the subject does not have many high frequency components. For example, when the face area of the subject detected through the FD function includes a background as well as the subject's face, back-focusing may occur in the digital image processing device due to high frequency information existing in the background. In another example, back-focusing may occur in the digital image processing device due to face shape information of the subject included in the face area of the subject.